1. Field of the Invention
The invention relates to a method of and an apparatus for ascertaining an rpm of an electric motor.
2. Description of the Prior Art
In many fields in technology, it is necessary to know a precise rpm or a precise rotary position of a motor. With direct current motors, for instance, it is known to detect the rpm, and various methods are used for this. One inexpensive variant is to calculate the rpm with the aid of Hall sensors; a Hall sensor detects the position of a rotor and sends that onward to a control unit. The Hall sensors react to the magnetic field of the rotating rotor, which is made of a magnetic material. For calculating the rpm, the time between two edges of a Hall signal is measured, and the rpm is calculated from that.
The object of the invention is to furnish a fast method for ascertaining an rpm and an apparatus for performing the method.